can you elaborate on the "peat soil" - tomato would prefer something not quite that acid - but if you're growing in pure peat that's definitely going to cause nutrient deficiencies of every shape and kind with time.

why the peat?indoors? no pests? not part of my experience with greenhouse growing.

you're growing tomatoes a full point lower than they like in a non-nutrient soil and looking for lack of ? nothing may be lacking - who knows at this point - perhaps everything is there except for the cultural conditions required by the tomato to utilize what is there?

if you are growing things indoors in a tightly controlled but artificial environment you will need to thoroughly pursue all the chemistry issues.